


A Certain Mental Fortitude

by pearl_o



Category: X-Men: First Class (2011) - Fandom
Genre: Charles is bossy in bed, Cunnilingus, Gay Mutant Road Trip, Gender or Sex Swap, M/M, Size Kink, Vaginal Sex, instructions
Language: English
Status: Completed
Published: 2015-04-19
Updated: 2015-04-19
Packaged: 2018-03-24 19:19:06
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,242
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/3781369
Author URL: https://archiveofourown.org/users/pearl_o/pseuds/pearl_o
Summary: <blockquote class="userstuff">
              <p>A mutant temporarily changes Charles's body, and Erik doesn't understand why Charles has taken a step back.</p><p>  <i>Charles sighs; he's been oblique partly out of consideration to Erik's sensibilities, but apparently Erik is going to make him spell it out. "I know you don't like women," he says gently.</i></p><p>  <i>Erik's expression doesn't change. "But you're not a woman."</i></p>
            </blockquote>





	A Certain Mental Fortitude

**Author's Note:**

> Write the porn you want to see in the word, they said. Well, okay. Shout-out to cygnaut and Unforgotten, in particular, for inspiring/encouraging this.

It's not as terrible as Charles would have imagined, truly. If it were in danger of being permanent, of course, that would be a much different story, but with the sulky mutant's assurance that the effects of his powers only ever lasted a week (confirmed by Charles's own panicked look through the young man's mind in that first frightened moment) -- well, it was uncomfortable, definitely. Unsettling. It's been two days, and each morning when he wakes up it takes a moment for his mind to catch up again to why his body feels so unfamiliar and _wrong_. But it's certainly not unbearable. He would classify it as more of a nuisance, really, and one he can handle for another five days.

He wouldn't mind if Erik would stop giving him those looks, though. Charles is handling all of this exceptionally well, if he _does_ say so himself, but it's taking a certain amount of mental fortitude. He doesn't have enough left over to handle Erik's reactions as well.

It seems strange to say he misses Erik, given that the last two days have been spent just like the weeks preceding: sharing a car, a hotel, and most of their time together. But in the nearly three weeks since that first kiss in the Virginia countryside, they haven't spent a single night where they haven't been intimate, sharing a bed and waking up together tangled in the covers.

The last two nights, Charles has gotten them separate rooms. 

Perhaps it would be different if Erik liked women -- it would be a once in a lifetime opportunity, wouldn't it, to see how different sex would be in a different body? Charles has seen it enough from women's minds, of course, but he's found the difference between reading others' experiences and going through it oneself is always subtly different.

But no. Charles is fairly certain Erik's tastes have never aligned that way. The first night they spent together, in the darkness of the room after, Erik had haltingly confessed his previous experience, as awkward, unsatisfying and far in-between as it had been, his mind flashing glimpses of memories that made Charles want to wince in sympathy and start making up for all the glorious orgasms Erik had been missing out on over the years.

Well, Charles had proceeded to do one of the two, at least.

And so that is yet another reason Charles will be grateful when this week is over: a return to waking up in Erik's arms, touching Erik freely, flirting whenever and however he wants. In the meantime... he'll deal with Erik's odd looks, just as he is dealing with the rest of it.

****

It doesn't quite turn out that way. Charles is beginning to notice a pattern in the way Erik always seems to surprise him and change his plan, going right back to the night they met. Tonight, when Charles exits the bathroom after his post-dinner shower, wrapped up in his fluffy bathrobe as always, he finds Erik sitting on the edge of the bed, frowning. 

It's been perhaps twenty minutes since Charles left Erik in the hallway, standing in front of the door to his own room. The surprise is a pleasant one. Maybe Erik's gotten past the worst of his discomfort, enough for them to have a drink and a game of chess. The thought makes Charles smile, but curiously Erik's scowl seems to deepen.

"Why have you been avoiding me?" Erik says, and Charles is so startled he stumbles over the edge of his robe before sitting down next to Erik with rather more force than he intends to.

"What? I haven't been!" Charles says. "I've just been-- giving you space, I suppose."

Erik's glare is harsh, but there's an element of vulnerability to it, too. Erik would hate to think that it wasn't hidden, Charles knows, that Charles doesn't need to go into his mind to read it. "Space? What sort of space? Is this-- Are you done with me, then?"

"Done with you?" Charles repeats, at a loss.

"Yes," Erik says, "done with me. With this." He waves a hand between them impatiently.

"No! No, no, no, of course not. Erik." Charles reaches out, sets his hand on Erik's thigh, the hard muscles tense beneath his palm. "That's the last thing I want."

A small bit of the anger seems to have subsided from Erik with his touch, but it's left a confusion in its place. "Then why--" Erik says, before cutting himself off and letting out a sharp exhale.

"Isn't it, well, obvious?" Charles says. He gestures down to himself -- the robe covers almost everything, but there's still enough flesh peeking out that one couldn't really mistake it. "I'll be back to normal soon enough, and I would very much like for us to carry on as we have been, but in the meantime..."

Erik looks at him blankly. "In the meantime, what?"

Charles sighs; he's been oblique partly out of consideration to Erik's sensibilities, but apparently Erik is going to make him spell it out. "I know you don't like women," he says gently.

Erik's expression doesn't change. "But you're not a woman."

Charles snorts and, rather than speak again, makes the same gesture to his body.

"I like _you_ ," Erik says in a low voice, and -- _oh_. Well. That's an interesting new sensation, isn't it, the way the rush of desire goes straight between his thighs, sudden heat that he can't help but clench against. 

"All right," Charles says, swallowing, "obviously my apprehensions were misplaced." 

There's not so much distance between them, and when Charles leans over there's none at all, meeting Erik in a kiss that starts soft but quickly becomes hungry. After a few minutes, Erik pushes at the collar of Charles's robe ,and Charles lets it fall to pool around his waist. 

Erik pulls back far enough to look, and Charles gives him some time to do so, trying to ignore his own impatience. In his own true body he is, he thinks, rather good at being naked, but as he's not used to this one yet, he can't say the same now. Erik's expression is just as inscrutable as the ones Charles has spent the last two days interpreting as unease, but Charles can still read the reassuring pulse of Erik's want in his mind. 

_You might have to show me what to do_ , Erik says, a faint whisper into Charles's mind.

Charles smiles. _I can do that_ , he responds, and he reaches out for Erik's hand to guide it to his breast.

***

Erik has lovely hands, strong and elegant, long-fingered. Charles noticed them from the first, when they were still wet and shivering on the Miami boat, just as he noticed more than a few of Erik's physical assets that his wetsuit put on prime display. It had been easy to dismiss such thoughts then, with so many important and life-changing things happening all at once, but the awareness had popped up again afterwards from time to time -- Erik moving a chess piece, tapping a pen against a piece of paper, clutching the steering wheel as he drove. They're at the forefront of Charles's mind now, lying under Erik in bed as they neck, Erik's fingers toying with his hard nipples, a little hesitant at first but with more and more confidence.

While Charles is completely naked, robe discarded to the carpet beside the bed, Erik has lost almost none of his clothes. Somewhere, in the back of Charles's mind, this seems incorrect. It's a chore to stop kissing long enough to say as much to Erik, but Charles forces himself. "Take off your clothes," he mumbles against Erik's cheek, stubble scratchy against his lips.

He imagines, suddenly, what it will feel like against the delicate skin of his inner thighs, and he can't help but move his hips, pushing up against the heavy weight of Erik's body. The feel of Erik's erection, hot and hard, only deepens the feelings. Charles can feel how wet he is already, the slickness almost dripping from him. If Erik moved his leg, Charles could get off that way, just grinding up against him, painting Erik's trousers with his juices.

It would be good, but it's not what he wants, so when Erik says, "You'll have to let go, if you want me to do that," Charles releases him from the grip his legs have around Erik's hips, with only a small amount of reluctance.

Erik always strips in the same manner: quick and efficient, with no wasted movements and no self-consciousness. Charles always enjoys the view, feeling almost greedy for the sight. On aesthetics alone, Erik is an exceptionally attractive man, and Charles would appreciate that even if his mind weren't as extraordinary and unexpected and unsought as it was, even if he didn't seem to somehow be another fraction of the same whole Charles was built from. But of course he is.

Erik's stiff cock points up toward his belly. Charles can't help but reflect, as he always does when faced with it head-on, on Erik's size. He'd said it out loud the first night -- _God, you're huge_ as Erik's trousers dropped, and Erik's face had turned a shocking bright red in response, even as his cock had twitched violently under Charles's regard. Charles hasn't said it since, but he thinks it each time.

He wants it inside him, but... not yet. First things first.

Charles holds his arms out, and Erik takes the invitation, crawling back up the bed and stopping to hold himself over Charles's body, looking down at him with a furrowed brow.

Charles spreads his legs so Erik can kneel between them. "Put your fingers inside me," Charles says. His voice sounds remarkably steady to his own ears. 

Erik takes a deep breath and lets his hand drift slowly from Charles's knee, up his thigh, and finally where Charles wants them, pushing into Charles with two of those long fingers. Charles can't quite swallow the noise that rises in his throat at the penetration; Erik's gaze flicks up immediately to meet Charles's.

"You're so slippery," Erik murmurs, sounding rather surprised about it. No wonder some of those previous experiences were so bad, Charles thinks with a helpless flash of sad humor before he pushes it away.

"That's what's going to let me take your cock," he tells Erik. His voice isn't _quite_ as composed as it was before. 

Erik makes a noise, somewhere between a grunt and a hum, and then he's looking down again between their bodies. Erik's had his fingers in Charles's ass quite a few times in these weeks, working him open to be fucked; he fucks Charles's cunt with his fingers now, a smooth and easy rhythm that Charles moves to meet. It feels wonderful, and Charles closes his eyes, arching his back and stretching his arms out above his head to hold onto the headboard behind him. But it's nowhere near enough to make him come, not with his clit still untouched and aching. And he does want, very badly, for Erik to fuck him properly, and between Erik's size and the fact that Charles has never done this before, it's clear to Charles what should happen next.

"Erik," Charles says urgently. 

Erik grunts, but his attention is still focused on the way his fingers are moving. Charles kicks his heel against the side of Erik's ribs to make him look up again, unspoken question in his eyes.

 _This_ , Charles says. He sends the image directly of what he wants: Erik's head between his thighs. It's visible when Erik swallows, his Adam's apple jumping a little in his throat, before he lies down on his stomach. Charles recognizes the soft sound of Erik holding back a groan as his cock rubs down against the mattress, half a thrust down before it's quickly aborted.

There's a long pause, while Charles forces himself not to push quite yet, and then Erik licks, a little too delicately, around his fingers still buried inside Charles. Charles's own hands ache a bit as he forces himself to unwrap them from the headboard, moving them down so he can bury his fingers in Erik's short, soft hair and guide him up to where Charles wants his mouth most desperately.

Charles has given his fair share of head over the years, and he knows how much things vary from person to person. He tries to pare it down to basics to share with Erik, keeping it simple; he doesn't want to overwhelm him, after all. But Erik is waiting for some sort of feedback; he may have been equally inexperienced with the first blowjob he gave Charles, but he had pushed forward then, eager and sloppy and experimenting, none of the uncertainty Charles can read off him now.

 _Keep licking me_ , Charles says, stroking his head. _I'll let you know when you're doing it right._

Charles's instructions, the bursts of sensation or wordless fondness and encouragement he sends to Erik's mind, and the feedback Erik is able to read from Charles's body himself, all working together. It takes a while before they find it, the right angle, the right pressure, the right rhythm, but when they do, Charles wants to scream. He's never been a screamer before, but perhaps that's another thing that's changed in this body.

 _If you stop, I'll kill you_ , Charles says, remembering how easy it always seemed to be for that steady climb to peter out. _Don't change a thing._ He's pulling too hard on Erik's hair, he knows, and his thighs are clamped like a vise around Erik's ears, heels dug in to Erik's back. He should do something about that, but he can't quite bring himself to care.

When he comes... well, if he _doesn't_ scream, it's a very, very close thing. 

Erik sits up, wiping his mouth with the back of his hand and breathing in gulps of air as Charles flops bonelessly back on the bed. Charles can feel the way Erik's scalp is stinging and his jaw aches, and he smiles up dopily as Erik shakes the cramp out of his hand. Erik's face is shiny, covered as it is with Charles's slick, and he's staring at Charles with that spooky intensity that always makes Charles shiver.

"Can I fuck you now?" Erik says, reaching to grope clumsily at one of Charles's tits again as he does, and Charles says immediately, "Oh god yes."

Erik is on top of him astonishingly quickly, kissing him desperately, sharing the taste that Charles is hard-pressed to accept as his own. His cock pushes between Charles's thighs, but the aim is wrong and he's thrusting through the slippery slide of the oversensitized flesh of Charles's vulva. It's sweet but so intense as to be almost painful, especially the pressure of Erik's cockhead against Charles's eager clit; even worse when Charles imagines what it must look like, the fat shaft nestled between his lips. He nips hard at Erik's swollen lower lip, and then licks it better in apology.

The second attempt is more successful, though even after everything, the penetration isn't effortless, Charles's cunt hesitating to allow the huge intruder access. The human body is a marvelous thing, though, adaptive as always, stretching and expanding until Erik is completely inside, leaving Charles utterly full from him. It's an amazing feeling -- Charles wishes he could bottle it, sell it, get drunk on it every night.

Erik nuzzles at Charles's throat. His hands are on Charles's wrists, tight but not painfully so, which is immensely satisfying in a way Charles doesn't completely understand. His first proper thrust, though, is much too hard, a violent jab, and Charles grunts in pain as he silently says hello to his cervix.

Erik goes still at Charles's cry. "Gentler," Charles explains to the top of Erik's head and the lovely expanse of his back, and he can see the deep breath that shakes through his body before Erik moves again, slower now and more deliberate, in great rippling waves. Charles is pleasantly aware of Erik's strength, his stamina, and the combination of noises in the room -- Erik's harsh, almost-pained-sounding breaths, the wet slap of their flesh together, the regular rock of the headboard against the wall with each of Erik's long, steady thrusts -- all seem designed to be exceptionally arousing. It's an awkward angle to get a hand between them, but Charles is fairly certain there's another climax in it for him, which is well worth any awkwardness.

Oh, and he's right: yes, yes, _yes_ , there it is, all the muscles in his body spasming and contracting in that glorious endless moment as he clenches down hard on Erik's beautiful dick.

Charles is surprised and a little confused when Erik pulls out (he feels so empty now, without him) and he watches speechlessly, as Erik rises up on his knees, hunching over himself with one hand on his balls and one hand jerking his cock. It's only a matter of moments before Erik reaches his peak as well. Charles doesn't know which to direction his attention to, Erik's handsome face twisted up in exquisite agony, or his pulsing cock and the way the long ropes of come spurt onto Charles's lower belly and pubic hair.

Once his breath is caught, Erik sinks to the mattress to lie down next to Charles, curling up close against him. 

Charles turns onto his side to face him. Erik's hair, so immaculate and carefully styled most of the time, is mussed, a sweaty lock falling into his eyes, which is something Charles always loves. He brushes it out of the way, now, and then strokes his hand down Erik's face. He sends an unformed question towards Erik's mind, curious.

"Isn't it obvious?" Erik says. Charles can tell he's fighting a yawn. "I didn't want to get you pregnant."

Charles laughs out loud, and Erik narrows his eyes in a way that would be a glare in any other situation. "That's very sweet," Charles explains, "but that's not something we have to worry about. If we do this again, feel free to not take those pains."

"If," Erik says, after a slight pause.

"Do you want to?"

Erik bites his lip -- the same place, Charles suspects, that he had nipped at earlier. "I thought I told you earlier," he says after a moment. "I don't want to be done with you."

It might be as close to a declaration as either of them has come, and even though Charles had already known how deep Erik's emotions run, had already known Erik felt the same amazement at finding another like oneself in the world, and that instant, strong connection -- despite all that, it still makes Charles's heart beat faster in his chest.

"You should sleep in here," Charles says. "The bed's too big for a single occupant."

The corner of Erik's mouth turns up in an almost-smirk. "Won't that scandalize the puritans in this town?"

"I couldn't care less," Charles says honestly, and the answer seems to please Erik; he leans forward to kiss Charles again.

In the morning when Charles wakes up, Erik is pressed warm all along Charles's back, one hand splayed out flat across Charles's stomach.

Four more days left, Charles remembers, until his outsides match him once more. 

Really, it's not very long, in the grand scheme of things.

**Works inspired by this one:**

  * [A Not-Bad Turn (the show me remix)](https://archiveofourown.org/works/4232769) by [Red](https://archiveofourown.org/users/Red/pseuds/Red)




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